单项选择题
A.3~3.5S B.6~7.5S C.10~11.5S D.19~20S
A.3~3.5S B.6~7.5S C.10~115S D.19~20s
A.引导螺母失效 B.调整螺母失效 C.膜板穿孔 D.皮碗破损